Process for evaporating refrigerant liquids



D 1929- s. c. CARNEY PROCESS FOR EVAPORATING.REFRIGERANT LIQUIDS Filed Nov. 26, 1926 inafter disclosed.

latented Dec. 17, 1929 UNITED STATES PATENT, oar-ice smarts. cmannv, or ruLs oxranoma, ASSIGNOR 'ro sHEILL PETROLEUM com PORATION, A eonroaarron or VIRGINIA PROCESS FOR EVAPORATIilI'G REFRIGERANT LIQUIDS Application filed November 26, 1926. Serial No. 150,760.

This invention relates to improvements ini processes for evaporating a refrigerant liq-1 uid, andconsists in the-novel procedure here-j In the ordinary flooded system of evapol ration of simple substances commonly used; as refrigerating agents, the refrigerant boils at a fixed temperature and produces a fixed cooling effect upon the load. In addition to the ordinary substances, such as ammonia, sulphurdioxide and carbondioxide and other refrigerating agents of uniform and fixed composition, it has been found that hydro-l carbon liquids made up of fractions having different boiling points are also desirable as refrigerating agents. The composite hydrocarbon liquids used as refrigerating liquids, however, essentially do not have a common, boiling point, but a boiling range due to the different boilin points of the fractions com-v posing the refrigerating liquid. The mixtures of hydrocarbon obtained as by-products from the stabilizers of known type for stabilizing the gasoline product and which, upon "condensation, are suitable. for refrigerating agents, ordinarily would have a substantial boiling range, for instance, from 20 degrees to 75 degrees Fahrenheit between" the initial and final boiling point of the. mixture.

It is the purpose of the present process tov provide a method of evaporating such refrigerating agents having a substantial boiling range, whereby, by proper control, the refrigerant may be evaporated at practically a con stant temperature.

The process may be better understood by reference to the a paratus employed and diagrammatically illustrated in the drawing.

The refrigerant to be evaporated is supplied from any suitable source through a supply pipe 1 which connects into a header 2 having connection with evaporating units that are spaced apart and arranged parallel with each other. The evaporation units comprise shells having a series of-inclined tubes 3 that connect into heads 4 and 5. The lower heads 4 are in communication With-the header 2, and the upper heads 5 are connected by pipes 6 into a tank 7, the pipes entering the tank substantially intermediate its height. A

pipe 8 leads from the bottom -of the. tank 7 and connects into theheader 2. There is a cross connection from the pipe 1 to the bottom of the tank 7 controlled by a valve 9.

The supply of the refrigerant liquid is controlled by a liquidlevel valve mechanism 10 which mechanism can be adjusted so that the height of the refrigerant in the base of the tank 7 may be held at a predetermined level.

The material being cooled, which may be either gas, gas and liquid mixed, or liquid alone, is admitted to the shell of the evaporating units through a supply pipe 11 that has branches 12 and 13 communicating respecwith whichthe vapor line is connected, the

purpose being to maintain a regulated back pressure in the W. or line.

The principle 0 the operation of the appa-. ratus described is that the refrigerant 1i uid is carried in the-tubes 3 and also a resi ual supply thereof carried in the lower a art of the tank 7, the upper part of the tan above the level of the liquid constituting a vapor chamber. The material to be cooled'circu lates downwardly over the tubes?) which heats the tubes throughout their len h, thereby causing the liquid within the tu es 3 to boil and the vapor which it gives ofl' entrains boiling liquid continuously leaves the inner sur face of the tube and travels upwardly through the central part thereof out of contaot'with its inner surface. There is thus discharged into the tank 7 through the pipes 6 mixed liquid and vapor which separate by gravity, the unevaporated liquid returning to the lower part of the tank 7 and the vapor accumulating in the head of the tank.

I am, of course, aware of processes for evaporating a refrigerant liquid having a fixed .boiling point according to the flooded system.

The problem, however, of the evaporation of a refrigerant in a flooded system having a boiling range is quite distinct from that of evaporating a refrigerant with a fixed boiling a point as it involves a different principle.

A refrigerant comprising components having different boiling points where part of the composite liquid remains in the liquid phase and'part passes into the vapor phase, and the liquid and vapor components are in intimate contact at any given combination of temperature and pressure, the composition of the liquid and'of the vapor in contact with it bear a definite relation to each other and the control factors of temperature and pressure do not act the same as they do in connection with a simple liquid used as .a refrigerant. As has heretofore been pointed out, simple refrigerants boil at a fixed temperature and their cooling effect is constant at a given-pressure,

.whereas in refrigerants having boiling range, the boiling points may be Varied by pres sure andby the amount of the composite mixture remaining in the liquid phase and that passing into the-vapor phase. The residual liquid, therefore, has a direct eflect upon the cooling action of the vaporization that results from a part of the liquid passing into a the vapor phase. In the case of a simple liquid the unevaporated portion has no effect on the temperature produced by the part thereof that passes into the vapor phase.

. Moreover, there is a distinct difference between a process of evaporating a refrigerant having a boiling range under conditions where part of the refrigerant remains in the liquid phase, and a process under which the composite refrigerant is evaporated by the expansion principle. In evaporating a composite refrigerant on the expansion principle "there is no equality of temperature in the refrigerating unit and there is no possibility of accurate control.

In the present process there is a decided practical advantage because of the increased rate of heat transfer secured, and the highly accurate and simple form of temperature con.- trol. This will be apparent from the consid eration of the operation of the process. In

the operation of the present process, if it be I assumed that the refrigerant made up of components having a boiling range is supplied in the pipe 1 and the entire refrigerating unit is empty, by manipulating a hand operated valve 20 the rate of evaporation can. be controlled so that only a part of the refrigerant- ],iquid will be evaporated. By continuing the ntroduction of the refrigerant liquid a quan- "sity of unevaporated liquid will accumulate until the liquid level thereof reaches a point for which the float mechanism 10 is set.

When this condition has been attained the material to be cooled is admitted to the shells of the evaporators and passed down exteriorally of the tubes '3 and toward the heads 4,

The refrigerant liquid will thereupon begin to boil and will reduce the residual liquid 'n the bottom of the tank 7. Upon the reducion of the liquid level the liquid control 10 peratestoadmit a further supply of the rerigerant liquid. When the temperature of t e material being cooled reaches a point for. hich the thermostat 17 isset, the thermostat will sufficiently close the pressure regulating lalve 18 to maintain a predetermined pressure on the evaporating liquid. This adjustment will permit the evaporation only of a sufl'icient amo unt of liquid to..maintain the temperature of the circulating unevaporated refrigerant to bring about the desired cooling action. a

The portion of the liquid that passes into the vapor phase is evacuated from the tank loo 7 and is compressed and constantly returned to the system so that the make-up of the refrigerant is continued uniform.

The component of the original mixture that passes into the vapor phase does so at a higher temperature or a lower temper ature' in the presence of the heavier liquid than if it were evaporated out of-the presence of the least volatile liquid. Therefore the component of the refrigerant remaining in the liquid phasedirectly effects the evapw rating of the component that passes into the vapor phase.

The component of the liquid that remains in the liquid phase constitutes a body through which the cooling effect, produced by the evaporation, is distributed equally through the cooling surfaces in the heat exchanger and this temperature will be uniform' throughout the entire refrigerating element.

Furthermore, the temperature produced by. the evaporation of the liquid that passes into the vapor phase is accurately controlled by j be produced.

I the thermostat thatregulates the back 4 pressure, which thermostat is within the direct and immediate influence of the productdischarged from the refrigerating unit. This is a matter ofconsiderable importance be cause any desired temperature within the boil ing range of the composite refrigerant can It will be understood that the vapor from the vapor line 19 is recondensed and returned to'the system in such a way as" to constitute the refrigerant supply entering the system.

through the pipe 1, except for such additherefore,- that the apparatus disclosed is 1' Patent is I 1. A process of refrigeration which consists tional flui lf'as may be required to maintain the necessary refrigerantsupplyp The process, therefore, may be operated economically and" with assurance of acon-f stant temperature exchange with the load. It is obyious also that the principle of the invention may be practiced, on apparatus of varioustypes'and This to be 11nderst0od,.

merely-Yin exemplification of an' operativeapparatus for the purpose of practicing the 25 I process of the invention.

What I claim and desire to secure by Letters in evaporating the lighter part'of a .liquid hydrocarbon refrigerant having components. of different relative volatility while main- "taining the other part of the refrigerant in the liquid phase; withdrawing the evaporated part; condensing said evaporated part and reintroducing the condensed part into the residual body of-the'liquid refrigerant.

2. A process of refrigeration vwhich cons'ists in circulatinga body. of hydrocarbon refrigerant, including components'having different boiling points, counter-current tothe fluid to be cooled; evaporating thereby a lighter part of the refri erant while main- 7 taining'the other part 0 the refrigerant in the liquid phase withdrawing the evaporated part; condensing said evaporated part; and

automatically controlling the reintroduction of the condensed part into the residual body of liquid-refrigerant. I

3. A process of refrigeration which consists'in evaporating the lighterportion of a liquid refrigerant, comprising a, mixture of volatile hydrocarbons, in the presence of an excess amount of the liquid remaining in the "points, in the presence of an excess amount of the liquid remaining in the liquid phase; removing the vapors; controlling the pressure on the liquid automatically in'relation to the temperature of the cooled product; and continually supplying to the frig'erant aquantity of liquid equal in weight and composition to the evaporated portion withdrawn, thereby automatically controlling the composition and amount of the circulating body of refrigerant. i

- v SAMUEL C, CARNEY,

ody of liquid re-- liquid phase; removing the vapors; control i ling thepressure on the' liquid automatically 'in relation to the temperature 'of the cooled product; and continually supplying to the body of the liquid refrigerant'a quantity of having different boiling evaporated portion withv 

